feat: add calendar screen

lib/i18n/en-US.i18n.yaml

@@ -48,7 +48,10 @@ nav:
   courseTable: Courses
   scores: Scores
   portal: Portals
+  calendar: Calendar
   profile: Me
+calendar:
+  month: Month
 courseTable:
   notFound: Course table not found
   dayOfWeek(map):

lib/i18n/strings.g.dart

@@ -4,7 +4,7 @@
 /// To regenerate, run: `dart run slang`
 ///
 /// Locales: 2
-/// Strings: 208 (104 per locale)
+/// Strings: 212 (106 per locale)
 
 // coverage:ignore-file
 // ignore_for_file: type=lint, unused_import

lib/i18n/strings_en_US.g.dart

@@ -44,6 +44,7 @@ class TranslationsEnUs extends Translations with BaseTranslations<AppLocale, Tra
 	@override late final _TranslationsIntroEnUs intro = _TranslationsIntroEnUs._(_root);
 	@override late final _TranslationsLoginEnUs login = _TranslationsLoginEnUs._(_root);
 	@override late final _TranslationsNavEnUs nav = _TranslationsNavEnUs._(_root);
+	@override late final _TranslationsCalendarEnUs calendar = _TranslationsCalendarEnUs._(_root);
 	@override late final _TranslationsCourseTableEnUs courseTable = _TranslationsCourseTableEnUs._(_root);
 	@override late final _TranslationsProfileEnUs profile = _TranslationsProfileEnUs._(_root);
 	@override late final _TranslationsEnrollmentStatusEnUs enrollmentStatus = _TranslationsEnrollmentStatusEnUs._(_root);
@@ -130,9 +131,20 @@ class _TranslationsNavEnUs extends TranslationsNavZhTw {
 	@override String get courseTable => 'Courses';
 	@override String get scores => 'Scores';
 	@override String get portal => 'Portals';
+	@override String get calendar => 'Calendar';
 	@override String get profile => 'Me';
 }
 
+// Path: calendar
+class _TranslationsCalendarEnUs extends TranslationsCalendarZhTw {
+	_TranslationsCalendarEnUs._(TranslationsEnUs root) : this._root = root, super.internal(root);
+
+	final TranslationsEnUs _root; // ignore: unused_field
+
+	// Translations
+	@override String get month => 'Month';
+}
+
 // Path: courseTable
 class _TranslationsCourseTableEnUs extends TranslationsCourseTableZhTw {
 	_TranslationsCourseTableEnUs._(TranslationsEnUs root) : this._root = root, super.internal(root);
@@ -395,7 +407,9 @@ extension on TranslationsEnUs {
 			'nav.courseTable' => 'Courses',
 			'nav.scores' => 'Scores',
 			'nav.portal' => 'Portals',
+			'nav.calendar' => 'Calendar',
 			'nav.profile' => 'Me',
+			'calendar.month' => 'Month',
 			'courseTable.notFound' => 'Course table not found',
 			'courseTable.dayOfWeek.sunday' => 'Sun',
 			'courseTable.dayOfWeek.monday' => 'Mon',

lib/i18n/strings_zh_TW.g.dart

@@ -45,6 +45,7 @@ class Translations with BaseTranslations<AppLocale, Translations> {
 	late final TranslationsIntroZhTw intro = TranslationsIntroZhTw.internal(_root);
 	late final TranslationsLoginZhTw login = TranslationsLoginZhTw.internal(_root);
 	late final TranslationsNavZhTw nav = TranslationsNavZhTw.internal(_root);
+	late final TranslationsCalendarZhTw calendar = TranslationsCalendarZhTw.internal(_root);
 	late final TranslationsCourseTableZhTw courseTable = TranslationsCourseTableZhTw.internal(_root);
 	late final TranslationsProfileZhTw profile = TranslationsProfileZhTw.internal(_root);
 	late final TranslationsEnrollmentStatusZhTw enrollmentStatus = TranslationsEnrollmentStatusZhTw.internal(_root);
@@ -186,10 +187,25 @@ class TranslationsNavZhTw {
 	/// zh-TW: '傳送門'
 	String get portal => '傳送門';
 
+	/// zh-TW: '行事曆'
+	String get calendar => '行事曆';
+
 	/// zh-TW: '我'
 	String get profile => '我';
 }
 
+// Path: calendar
+class TranslationsCalendarZhTw {
+	TranslationsCalendarZhTw.internal(this._root);
+
+	final Translations _root; // ignore: unused_field
+
+	// Translations
+
+	/// zh-TW: '月'
+	String get month => '月';
+}
+
 // Path: courseTable
 class TranslationsCourseTableZhTw {
 	TranslationsCourseTableZhTw.internal(this._root);
@@ -580,7 +596,9 @@ extension on Translations {
 			'nav.courseTable' => '課表',
 			'nav.scores' => '成績',
 			'nav.portal' => '傳送門',
+			'nav.calendar' => '行事曆',
 			'nav.profile' => '我',
+			'calendar.month' => '月',
 			'courseTable.notFound' => '找不到課表',
 			'courseTable.dayOfWeek.sunday' => '日',
 			'courseTable.dayOfWeek.monday' => '一',

lib/i18n/zh-TW.i18n.yaml

@@ -48,7 +48,10 @@ nav:
   courseTable: 課表
   scores: 成績
   portal: 傳送門
+  calendar: 行事曆
   profile: 我
+calendar:
+  month: 月
 courseTable:
   notFound: 找不到課表
   dayOfWeek(map):

lib/router/app_router.dart

@@ -5,6 +5,7 @@ import 'package:tattoo/repositories/auth_repository.dart';
 import 'package:tattoo/shells/animated_shell_container.dart';
 import 'package:tattoo/screens/main/home_screen.dart';
 import 'package:tattoo/screens/main/portal/portal_screen.dart';
+import 'package:tattoo/screens/main/calendar/calendar_screen.dart';
 import 'package:tattoo/screens/main/profile/about_screen.dart';
 import 'package:tattoo/screens/main/profile/profile_screen.dart';
 import 'package:tattoo/screens/main/score/score_screen.dart';
@@ -19,6 +20,7 @@ abstract class AppRoutes {
   static const home = '/';
   static const score = '/score';
   static const portal = '/portal';
+  static const calendar = '/calendar';
   static const profile = '/profile';
   static const intro = '/intro';
   static const login = '/login';
@@ -105,6 +107,15 @@ GoRouter createAppRouter({
             ),
           ],
         ),
+        StatefulShellBranch(
+          routes: [
+            GoRoute(
+              path: AppRoutes.calendar,
+              pageBuilder: (context, state) =>
+                  const NoTransitionPage(child: CalendarScreen()),
+            ),
+          ],
+        ),
         StatefulShellBranch(
           routes: [
             GoRoute(

lib/screens/main/calendar/calendar_providers.dart

@@ -0,0 +1,135 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:tattoo/database/database.dart';
+import 'package:tattoo/repositories/calendar_repository.dart';
+
+// ---------------------------------------------------------------------------
+// Shared notifier — used for both focused-day and selected-day providers.
+// ---------------------------------------------------------------------------
+
+class DateTimeNotifier extends Notifier<DateTime> {
+  @override
+  DateTime build() => DateTime.now();
+  void updateDate(DateTime day) => state = day;
+}
+
+final calendarFocusedDayProvider = NotifierProvider<DateTimeNotifier, DateTime>(
+  DateTimeNotifier.new,
+);
+
+final calendarSelectedDayProvider =
+    NotifierProvider<DateTimeNotifier, DateTime>(DateTimeNotifier.new);
+
+// ---------------------------------------------------------------------------
+// Calendar event display helpers
+// ---------------------------------------------------------------------------
+
+extension CalendarEventX on CalendarEvent {
+  /// The inclusive last day/time of this event for display and bucketing.
+  ///
+  /// For all-day events the portal stores `end` as the exclusive next-day
+  /// midnight (e.g. an event on Jan 5 has end = Jan 6 00:00:00). We subtract
+  /// 1 ms so that bucketing treats Jan 5 as the last day, not Jan 6.
+  ///
+  /// For timed events the raw `end` is used as-is.
+  ///
+  /// Note: the DB overlap query in CalendarRepository._eventsOverlapping uses
+  /// the raw `end` column, so boundary-events may appear in a wider DB slice
+  /// than the bucketing below. This intentional mismatch is safe — the display
+  /// layer only places events in the correct day buckets.
+  ///
+  /// Precondition: callers in [calendarEventsProvider] guard `event.start != null`
+  /// before calling this getter.
+  DateTime get displayEndDate {
+    final e = end;
+    if (e == null) return start!; // start is non-null at this call site
+
+    if (allDay) {
+      // All-day end is the exclusive next-day midnight; subtract 1 ms to keep
+      // it within the correct day.
+      final startDay = DateTime(start!.year, start!.month, start!.day);
+      final endDay = DateTime(e.year, e.month, e.day);
+      return endDay.isAfter(startDay)
+          ? endDay.subtract(const Duration(milliseconds: 1))
+          : startDay;
+    }
+
+    return e;
+  }
+}
+
+// ---------------------------------------------------------------------------
+// Range notifier — tracks the ±1-month window around the focused month.
+// ---------------------------------------------------------------------------
+
+/// Returns a [DateTimeRange] spanning from the start of the month before
+/// [focus] to the end of the month two months after [focus].
+///
+/// Uses Dart's normalising DateTime constructor (day 0 = last day of the
+/// previous month) to keep the arithmetic simple and correct across year
+/// boundaries (e.g. month - 1 when month == 1 yields December of the
+/// previous year).
+DateTimeRange threeMonthWindow(DateTime focus) {
+  return DateTimeRange(
+    start: DateTime(focus.year, focus.month - 1, 1),
+    end: DateTime(focus.year, focus.month + 2, 0),
+  );
+}
+
+class CalendarRangeNotifier extends Notifier<DateTimeRange> {
+  @override
+  DateTimeRange build() => threeMonthWindow(DateTime.now());
+  void updateRange(DateTimeRange range) => state = range;
+}
+
+final calendarRangeProvider =
+    NotifierProvider<CalendarRangeNotifier, DateTimeRange>(
+      CalendarRangeNotifier.new,
+    );
+
+// ---------------------------------------------------------------------------
+// Events provider — maps normalized date integers to event lists.
+// ---------------------------------------------------------------------------
+
+/// Encodes a calendar date as a compact integer key to avoid the pitfall of
+/// using [DateTime] objects (which include a time component) as map keys.
+int dateKey(int year, int month, int day) => year * 10000 + month * 100 + day;
+
+final calendarEventsProvider = FutureProvider<Map<int, List<CalendarEvent>>>((
+  ref,
+) async {
+  final range = ref.watch(calendarRangeProvider);
+  final repo = ref.watch(calendarRepositoryProvider);
+
+  final events = await repo.getCalendar(
+    startDate: range.start,
+    endDate: range.end,
+  );
+
+  final map = <int, List<CalendarEvent>>{};
+  for (final event in events) {
+    if (event.start == null) continue;
+
+    var current = DateTime(
+      event.start!.year,
+      event.start!.month,
+      event.start!.day,
+    );
+    final adjustedEnd = event.displayEndDate;
+
+    // If start and end coincide (zero-duration event), emit for exactly one day.
+    final lastDay = adjustedEnd.isBefore(current) ? current : adjustedEnd;
+    final last = DateTime(lastDay.year, lastDay.month, lastDay.day);
+
+    while (!current.isAfter(last)) {
+      map
+          .putIfAbsent(
+            dateKey(current.year, current.month, current.day),
+            () => [],
+          )
+          .add(event);
+      current = DateTime(current.year, current.month, current.day + 1);
+    }
+  }
+  return map;
+});